Almishal Saeed S I, Furst Matthew, Tan Yueze, Sivak Jacob T, Bejger Gerald, Petruska Joseph, Ayyagari Sai Venkata Gayathri, Srikanth Dhiya, Alem Nasim, Rost Christina M, Sinnott Susan B, Chen Long-Qing, Maria Jon-Paul
Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, USA.
Department of Chemistry, The Pennsylvania State University, University Park, PA, USA.
Nat Commun. 2025 Sep 2;16(1):8211. doi: 10.1038/s41467-025-63567-z.
High-entropy oxide (HEO) thermodynamics transcend temperature-centric approaches, spanning a multidimensional landscape where oxygen chemical potential plays a decisive role. Here, we experimentally demonstrate how controlling the oxygen chemical potential coerces multivalent cations into divalent states in rock salt HEOs. We construct a preferred valence phase diagram based on thermodynamic stability and equilibrium analysis, alongside a high throughput enthalpic stability map derived from atomistic calculations leveraging machine learning interatomic potentials. We identify and synthesize seven equimolar, single-phase rock salt compositions incorporating Mn, Fe, or both, as confirmed by X-ray diffraction and fluorescence. Energy-dispersive X-ray spectroscopy confirms homogeneous cation distribution, whereas X-ray absorption fine structure analysis reveals predominantly divalent Mn and Fe states, despite their inherent multivalent tendencies. Ultimately, we introduce oxygen chemical potential overlap as a key complementary descriptor for predicting HEO stability and synthesizability. Although we focus on rock salt HEOs, our methods are chemically and structurally agnostic, providing a broadly adaptable framework for navigating HEOs thermodynamics and enabling a broader compositional range with contemporary property interest.
高熵氧化物（HEO）热力学超越了以温度为中心的方法，涵盖了一个多维领域，其中氧化学势起着决定性作用。在此，我们通过实验证明了控制氧化学势如何迫使岩盐型高熵氧化物中的多价阳离子转变为二价态。我们基于热力学稳定性和平衡分析构建了一个优选价态相图，以及一个通过利用机器学习原子间势的原子计算得出的高通量焓稳定性图。通过X射线衍射和荧光确认，我们识别并合成了七种包含锰、铁或两者的等摩尔单相岩盐成分。能量色散X射线光谱证实了阳离子分布均匀，而X射线吸收精细结构分析表明，尽管锰和铁具有固有的多价倾向，但主要呈现二价态。最终，我们引入氧化学势重叠作为预测高熵氧化物稳定性和可合成性的关键补充描述符。尽管我们专注于岩盐型高熵氧化物，但我们的方法在化学和结构上具有通用性，为探索高熵氧化物热力学提供了一个广泛适用的框架，并能够实现具有当代性能兴趣的更广泛成分范围。
